Preparation of activated carbon from lignin by chemical activation

Activated carbons were prepared from lignin by chemical activation with ZnCl2, H3PO4 and some alkali metal compounds. The influence of carbonization and activating reagent on the pore structure of the activated carbon was investigated. It was found that the maximum surface areas were obtained at the carbonization temperature of 600°C in both ZnCl2 and H3PO4 activation, and that the surface areas were as large as those of the commercial activated carbons. On the other hand, in alkali metal activation it was found that the maximum surface areas were obtained at the carbonization temperature of 800°C. Except for Na2CO3 maximum surface areas were much larger than those of the commercial activated carbons. The activated carbon prepared by K2CO3 activation showed a surface area of nearly 2000 m2/g. It was shown that ZnCl2 works effectively as dehydration reagent below 600°C. On the other hand, K2CO3 works effectively in two temperature ranges, below 500°C and above 600°C. Below 500°C, the carbonization behavior was modified by impregnation with K2CO3, but the pore structure changes little. Above 600°C, carbon was consumed by K2CO3 reduction and then the surface area was increased.